The present invention relates generally to electromagnetic resolvers, and more particularly, to phase compensation for electromagnetic angle resolvers.
Electromagnetic angle resolvers provide mechanical shaft angle data to electronic circuits by means of electric signals. In a typical complex system, many such resolvers are used. Conventional compensation techniques required a separate excitation power amplifier to drive the primary winding of each resolver. The demodulation or decoding of the signals from each resolver is typically synchronized to the signal used to excite the resolver. However, the resolver output signals (sine and cosine) are inadvertently phase shifted with respect to the resolver excitation signal, which reduces angle measurement accuracy. The phase shift of the resolver output signals also changes with temperature.
The simplest approach used in the prior art was to do nothing to correct the phase shift problem, and therefore accept the resulting resolver inaccuracies. Other conventional compensation methods employed an additional compensation winding in the resolver, hardware to receive the compensation signal generated by the additional compensation winding, and separate closed-loop, stability-compensated feedback amplifiers for each resolver primary. This extra hardware resulted in lower system performance and higher system cost.
Accordingly, it is an objective of the present invention to provide phase compensation for electromagnetic angle resolvers that does not require additional windings and associated amplification circuitry and which allows a single excitation power amplifier to drive all the resolver primary windings.